Seismic imaging using wave equation extrapolation

Abstract

A method for producing seismic images from seismic data obtained from two different datums. Traveltimes between the two datums are determined from either measurements or an assumed velocity field. An extrapolation of the data to simulated source and receiver locations is carried out using any form of the wave equation which does not require velocity field information. After extrapolation, the data at the simulated source and receiver locations is processed using standard seismic imaging techniques. The method can be applied to simulate borehole, crosshole, or multi-borehole seismic data.

What is claimed is: 
     
       1. A method of imaging a geological feature, comprising the steps of: (a) specifying two data acquisition datums, a first data acquisition datum coincident with a first borehole and a second data acquisition datum coincident with a second borehole;   (b) obtaining seismic data from a family of sources placed within said first borehole and a family of receivers placed within said second borehole;   (c) specifying two imaging datums, a first imaging datum coincident with the surface of the earth and proximate to said first borehole and a second imaging datum coincident with said surface and proximate to said second borehole, wherein a line coincident with said second imaging datum extends substantially colinear with said first imaging datum and sequentially through said second borehole, said first borehole, and said first imaging datum;   (d) wave equation extrapolating said family of sources to said first imaging datum using traveltimes calculated from a first velocity model;   (e) wave equation extrapolating said family of receivers to said second imaging datum using traveltimes calculated from a second velocity model; and   (f) imaging said feature using said extrapolated sources and receivers.